Mortar composition containing iron oxide

ABSTRACT

A mortar composition, which includes (i) a treated palm oil fuel ash, wherein the treated palm oil fuel ash is the only binder present, (ii) a fine aggregate, (iii) an alkali activator containing an aqueous solution of sodium hydroxide and sodium silicate, and (iv) aluminum hydroxide as a strength enhancer. A cured mortar made from the mortar composition is also disclosed with advantageous compressive strength properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No.16/522,200, now U.S. Pat. No. 11,168,027, having a filing date of Jul.25, 2019, the entire contents of which are incorporated herein byreference.

STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTORS

Aspects of this technology are described in an article “Impact ofAl(OH)₃ addition to POFA on the compressive strength of POFAalkali-activated mortar” by Babatunde Abiodun Salami, Megat Azmi MegatJohari, Zainal Arifin Ahmad, Mohammed Maslehuddin, and Adeshina AdewaleAdewumi, in Construction and Building Materials, 2018, 190, pg. 65-82,which is incorporated herein by reference in its entirety.

BACKGROUND OF THE DISCLOSURE Technical Field

The present disclosure relates to mortar compositions, specificallyalkali-activated mortar compositions that include palm oil fuel ash, andcured mortar made therefrom.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentdisclosure.

The cement industry has begun research into energy efficientcementitious materials to replace ordinary Portland cement (OPC). CO₂ isa byproduct produced during the production of Portland cement,specifically during the formation of clinker (intermediate product)using elevated temperatures inside a kiln, where calcium carbonate fromcalcium-rich material is converted into lime and CO₂. Therefore, inefforts to reduce or replace cement, and thus lower CO₂ emissions, thecement industry has turned to aluminosilicate binders usingalkali-activated cement technologies, owing in part to the vastaluminosilicate material options.

Aluminosilicate materials are classified broadly into low and highcalcium aluminosilicate materials based on the calcium oxide (CaO)content of these materials. The amount of CaO in these materialsdictates the alkalinity level of the activator required for activationand the curing type necessary for the hardening process. With lowcalcium materials, such as metakaolin and other materials, a higherconcentration of alkaline activators and thermal curing is often neededin order to enhance the reaction rate and ensure proper densification ofthe binder microstructure. However, when the calcium content is high,such as in fly ash, lower alkaline activator molarities and lowertemperature curing can be used in the activation process to provideadequate hardening. Apart from CaO, alumina (Al₂O₃) is anotherconstituent oxide involved in the alkali-activated binderstrength-forming process. As a result, aluminosilicate materials havinga low content of Al₂O₃ can greatly affect the microstructural propertiesof the binder, which by extension can affect the mechanical strengthproperties and durability performance of the alkali-activated binder.Al₂O₃ accelerates the setting of the alkali-activated binder while thesetting of the alkali-activated binder is inhibited with increasing SiO₂content. Palm oil fuel ash (POFA), for example, is characterized by highSiO₂ and low Al₂O₃ content, making it a non-obvious choice for use as abinder material.

POFA is an agricultural waste byproduct that has been historicallydumped into fields indiscriminately, causing lost profits and healthconcerns to nearby inhabitants. Finding constructive and profitable usesfor POFA thus remains of interest. However, the use of POFA as a bindingmaterial in cement/mortar has significant challenges. For instance, thechemical composition of POFA is characterized by a high amount of SiO₂(in varying quantities depending on the region and treatment), and lowquantities of Al₂O₃ and CaO, which greatly affects the engineeringproperties of POFA. This Al₂O₃ deficiency results in a slow rate ofcondensation reactions owing to the formation of more Si—O—Si bonds andfewer Si—O—Al bonds. In fact, two important parameters used byresearchers to gauge effective binding materials are the SiO₂/Al₂O₃ratio and the CaO content. The low alumina content in POFA is a hugehindrance for using POFA as a binder, as it causes inadequacies inSiO₂—Al₂O₃ bond formation needed for high strength.

In view of the forgoing, one object of the present disclosure is toprovide mortar compositions that contain palm oil fuel ash (POFA), andcured mortars made therefrom with advantageous compressive strength anddurability properties. Such mortar compositions may be made with POFA asthe only binder material, which has the benefit of reducing POFA wastevolumes in landfills, conserving natural materials, and reducing CO₂emissions and energy consumption required for cement manufacture.

BRIEF SUMMARY OF THE DISCLOSURE

According to a first aspect, the present disclosure provides a mortarcomposition that includes (i) a treated palm oil fuel ash, wherein thetreated palm oil fuel ash is the only binder present, (ii) a fineaggregate, (iii) an alkali activator containing an aqueous solution ofsodium hydroxide and sodium silicate, and (iv) aluminum hydroxide.

In some embodiments, the treated palm oil fuel ash is present in anamount of 20 to 30 wt. %, based on a total weight of the mortarcomposition.

In some embodiments, the treated palm oil fuel ash is obtainedsequentially from drying raw palm oil fuel ash at 80 to 120° C., sievingto a particle size of less than 300 μm, a first mechanical ball milling,calcining at 500 to 600° C., and a second mechanical ball milling.

In some embodiments, the treated palm oil fuel ash has a median particlesize (d₅₀) of 0.5 to 2.0 μm.

In some embodiments, the treated palm oil fuel ash contains, asconstituent oxides, 60 to 72 wt. % SiO₂, 4 to 8 wt. % Al₂O₃, 3 to 7 wt.% Fe₂O₃, 3 to 8 wt. % CaO, 1 to 5 wt. % MgO, 3 to 7 wt. % K₂O, 0.2 to0.5 wt. % SO₃, 0.1 to 0.25 wt. % Na₂O, and 1 to 5 wt. % of P₂O₃, eachbased on a total weight of the treated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash contains, asconstituent oxides, 66 to 68 wt. % SiO₂, 6 to 7 wt. % Al₂O₃, 5 to 6.5wt. % Fe₂O₃, 5 to 6 wt. % CaO, 2.5 to 3.5 wt. % MgO, 4.5 to 6 wt. % K₂O,0.3 to 0.35 wt. % SO₃, 0.18 to 0.2 wt. % Na₂O, and 3 to 4 wt. % of P₂O₃,each based on a total weight of the treated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash has a loss onignition (LOI) of less 3 wt. %, based on a total weight of the treatedpalm oil fuel ash, and a specific surface area of 1.4 to 1.6 m²/g.

In some embodiments, a weight ratio of the fine aggregate to the treatedpalm oil fuel ash is 1:1 to 2:1.

In some embodiments, the fine aggregate has a fineness modulus of 1.8 to2.1 and a saturated surface dry (SSD) specific gravity of 2.5 to 2.7.

In some embodiments, the fine aggregate is dune sand.

In some embodiments, a weight ratio of the alkali activator to thetreated palm oil fuel ash is 0.3:1 to 0.7:1.

In some embodiments, a weight ratio of sodium silicate to sodiumhydroxide is 1:1 to 3:1.

In some embodiments, the alkali activator is formed from an aqueoussolution of sodium hydroxide having a sodium hydroxide concentration of10 to 12 mol/L.

In some embodiments, a weight ratio of the aluminum hydroxide to thetreated palm oil fuel ash is 0.01:1 to 0.05:1.

In some embodiments, the aluminum hydroxide is the only strengthenhancer present.

In some embodiments, the mortar composition has weight ratio of water tothe treated palm oil fuel ash of 0.2 to 0.98.

In some embodiments, mortar composition consists of the treated palm oilfuel ash, the fine aggregate, sodium hydroxide, sodium silicate,aluminum hydroxide, and water.

According to a second aspect, the present disclosure provides a curedmortar containing the mortar composition in cured form.

In some embodiments, the cured mortar has a 28 day compressive strengthof 25 to 36 MPa.

In some embodiments, the cured mortar has a 28 day compressive strengthof 30 to 35.6 MPa.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is an image of typical palm oil fuel ash (POFA) dumping site nearto palm oil mill;

FIG. 2 is a flowchart for a treatment and production process for makingtreated POFA (TPOFA) used in the mortar composition;

FIG. 3 is an image of raw POFA loaded into an oven for drying;

FIG. 4 is a pictorial view of a mechanical ball mill with two millsoperating simultaneously;

FIG. 5 is an image of ground POFA after oven drying and grinding butbefore heat treatment in a gas-operated furnace, where the POFA has ablack appearance;

FIG. 6 is an image of calcined POFA (after heat treatment in agas-operated furnace), where the POFA has a grey appearance;

FIG. 7 is a graph showing the gradation of a fine aggregate used in theExamples.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure will now be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all of the embodiments of the disclosure are shown.

Definitions

As used herein, the terms “optional” or “optionally” means that thesubsequently described event(s) can or cannot occur or the subsequentlydescribed component(s) may or may not be present (e.g. 0 wt %).

The phrase “substantially free”, unless otherwise specified, describes aparticular component being present in an amount of less than about 1 wt.%, preferably less than about 0.5 wt. %, more preferably less than about0.1 wt. %, even more preferably less than about 0.05 wt. %, yet evenmore preferably 0 wt. %, relative to a total weight of the compositionbeing discussed.

The term “comprising” is considered an open-ended term synonymous withterms such as including, containing or having and is used herein todescribe aspects of the invention which may (or may not) includeadditional components, functionality and/or structure. Terms such as“consisting essentially of” are used to identify aspects of theinvention which exclude particular components that are not explicitlyrecited in the claim but would otherwise have a material effect on thebasic and novel properties of the mortar composition in either a dry,wet or cured form. Basic and novel properties of the present disclosureinclude, but are not limited to, the strength such as compressivestrength, curing time, slump, workable flow, and viscosity. The term“consisting of” describes aspects of the invention in which only thosefeatures explicitly recited are included and thus other components notexplicitly or inherently included are excluded.

As used herein, the term “binder” refers to a composition or substancewith one or more constituents that is capable of binding materialstogether, once set. While a “binder” classically refers to materials ormixtures of materials that are “cements” (e.g., Portland cement), in thepresent disclosure, a “binder” may be a cement or any other materialthat is capable of forming cement or capable of forming materials withcement-like binding properties. Therefore, included in the definition of“binder” are those materials that have little to no cementitious valueby themselves but which will, in finely divided form and in the presenceof water, react chemically with certain chemicals present in the mortarcomposition to form compounds possessing cementitious properties. Forexample, pozzolans and burned organic matter residues (e.g. fly ash,silica fume from silicon smelting, highly reactive metakaolin, palm oilfuel ash, date palm ash, etc.), while not considered “cements”, areconsidered to be “binders” in the present disclosure.

As used herein, “mortar” refers to a thick mixture comprising water,fine aggregate, and binder, which is useful for holding buildingmaterials such as brick or stone together, for example. Mortar differsfrom concrete in that it does not include a coarse aggregate such asrock chippings, gravel, etc., and thus tends to be used as a glueelement, and not as a structural element as is common with concrete.

Mortar Compositions

In an effort to reduce CO₂ emissions, the cement industry has turned toreplacing cement binders such as ordinary Portland cement with low costburned agricultural waste products possessing binding properties.However, even when used as a partial cement replacement, such burnedagricultural waste products often provide inadequate strength properties(e.g., compressive strength) to the concrete or mortar, once cured. Suchinadequacies are exacerbated when attempting to completely replacecement with burned agricultural waste products.

Thus, the present disclosure provides a mortar composition (specificallyan alkali-activated mortar, AAM) in which the only binder present is atreated palm oil fuel ash, and which sets into a high compressivestrength cured mortar. The mortar composition generally comprises,consists essentially of, or consists of a treated palm oil fuel ash asbinder, a fine aggregate, an alkali activator of sodium hydroxide andsodium silicate, aluminum hydroxide, and water. The mortar compositionmay optionally contain one or more additives such as an accelerator, aretarder, a plasticizer (e.g., a superplasticizer), a pigment, acorrosion inhibitor, and a bonding agent.

Palm Oil Fuel Ash (POFA)

The oil palm is a tall-stemmed tree which belongs to the familyArecaceae (commonly known as palms). Oil palm trees, primarily theAfrican oil palm Elaeis guineensis, and to a lesser extent the Americanoil palm Elaeis oleifera and the maripa palm Attalea maripa, arecultivated for their palm oil producing fruit. The countries in theequatorial belt that cultivate oil palm are Benin Republic, Colombia,Ecuador, Nigeria, Zaire, Malaysia, and Indonesia, of which Malaysia isthe largest producer of palm oil and palm oil products (around 47-51% ofthe worlds exports of palm oil). In the palm oil industry, palm oil isextracted from the fruit and copra of the palm oil tree. After theextraction process, waste products such as palm oil fibers, shells, andempty fruit brunches are burned as biomass boiler fuel at 800 to 1,000°C. to boil water, which generates steam to power a turbine for supplyingelectrical energy to the entire palm oil mill extraction process.Usually, the palm oil waste product burned in the boiler is made up ofabout 85% palm oil fibers and about 15% shells and empty fruit bunches,although these percentages may vary. The resulting ashy, combustionbyproduct is palm oil fuel ash (POFA), which constitutes about 5 wt. %of solid waste products formed during palm oil processing. POFA does nothave sufficient nutrient value to be used as fertilizer and hastraditionally been disposed in open fields (profitless).

The inventors have found that palm oil fuel ash, specifically palm oilfuel ash which is treated in a certain way, can be used as a fullreplacement binder for cement in mortar compositions without adverselyaffecting the compressive strength of the cured mortar, when used incombination with an alkali activator and an aluminum hydroxide strengthenhancer.

‘Raw’ palm oil fuel ash, that is, palm oil fuel ash as it isformed/received from the oil palm boiler, typically has too high acarbon content (caused by incomplete burning of the residue) for use asan acceptable binder. Raw POFA typically also has a high moisturecontent of from 3 to 19 wt. %, or 4 to 15 wt. %, or 5 to 10 wt. % water,based on a total weight of the POFA, and a relatively large particlesize, for example a median particle size (d₅₀) of 55 to 75 μm,preferably 60 to 70 μm, preferably 64 to 66 μm.

In preferred embodiments, the palm oil fuel ash utilized herein istreated palm oil fuel ash, which is palm oil fuel ash which has beensubjected to a combination of drying, sieving, ball milling, andcalcining. Briefly, treated palm oil fuel ash may be formed according tothe following procedure.

The raw palm oil fuel ash obtained from a palm oil production facility(e.g., palm oil mill, United Oil Palm Industries Sdn. Bhd. in NibongTebal, Penang, Malaysia) may first be dried, for example, in an oven at80 to 120° C., preferably 90 to 110° C., preferably 95 to 105° C.,preferably about 100° C., to reduce the moisture content to below 5 wt.%, preferably below 4 wt. %, preferably below 3 wt. %, preferably below2 wt. %, preferably below 1 wt. %. The raw palm oil fuel ash may bedried for any amount of time that provides an adequately dried product,typically, for drying times of 12 to 48 hours, preferably 16 to 36hours, preferably 20 to 30 hours, preferably 24 hours.

The resulting dried palm oil fuel ash may then be subjected to sievingthrough one or more sieves of different size, preferably two or moresieves of different size, for example, sequentially through sieves ofdecreasing size to remove coarser and unwanted particulates. Inpreferred embodiments, the dried palm oil fuel ash is sievedsequentially through sieves of decreasing size, preferably through a setof two sieves of decreasing size, to provide sieved POFA having aparticle size of less than 400 μm, preferably less than 350 μm,preferably less than 300 μm. For example, the dried POFA may be sievedsequentially through a set of 600 μm and 300 μm sieves, to providesieved POFA containing no particles above 300 μm.

The resulting sieved palm oil fuel ash may then be subjected to a firstmechanical ball milling procedure to reduce the particle size and/or toincrease the surface area of the ash. Any type of ball milling apparatusknown to ordinary skill in the art may be employed, including, but notlimited to, a standard ball mill, a planetary mill, a vibration mill, anattritor—stirring ball mill, a pin mill, or a rolling mill. The vialsand balls used for the ball milling may be individually selected fromagate (cryptocrystalline silica), corundum (Al₂O₃), zirconium oxide(ZrO₂), stainless steel (Fe, Cr, Ni), tempered steel (Fe, Cr), andtungsten carbide (WC), preferably stainless steel (e.g., SS 316). Insome embodiments, the balls employed in the ball milling operation havea size of from 6 to 32 mm, preferably 8 to 28 mm, preferably 10 to 24mm, preferably 12 to 20 mm, preferably a variety of ball sizes areemployed for the ball milling operation.

The following ball milling parameters may be utilized. The ball topowder ratio (BPR) or charge ratio represents the weight ratio of themilling balls to the POFA charge. Various BPRs may be employed, buttypically a BPR may range from 1:1 to 10:1, preferably 2:1 to 9:1,preferably 3:1 to 8:1, preferably 4:1 to 7:1, preferably 5:1 to 6:1. Thesieved palm oil fuel ash may be ball milled at a rotational speed of 100to 600 rpm, preferably 120 to 500 rpm, preferably 140 to 400 rpm,preferably 160 to 300 rpm, preferably 180 to 200 rpm. The milling timemay also influence the product morphology and particle size. Suitablemilling times that may be practiced herein range from 15 minutes to 8hours, preferably 30 minutes to 6 hours, preferably 1 to 5 hours,preferably 1.5 to 4.5 hours, preferably about 2 to 4 hours, althoughshorter or longer milling times may also be practiced. Further, thesieved palm oil fuel ash may be ball milled in various atmospheres, forexample, in some embodiments, ball milling is performed in air (or agenerally oxygen-containing atmosphere, e.g., which includes anyatmosphere that contains at least 20%, preferably at least 40%,preferably at least 60%, preferably at least 80%, preferably at least90%, preferably at least 95%, preferably at least 99%, or about 100%oxygen by volume). Alternatively, ball milling may be carried out underan inert atmosphere such as under nitrogen or argon, preferably argon.The resulting product may be referred to herein as ground palm oil fuelash or “GPOFA”. In general, the GPOFA has a median particle size (d₅₀)of 2.8 to 3.5 μm, preferably 2.9 to 3.1 μm, preferably 2.96 to 3.0 μm.

At this stage, GPOFA still contains a relatively high amount of unburnedcarbon, with a loss on ignition (LOI) of greater than 8 wt. %, orgreater than 9 wt. %, or greater than 10 wt. %, and a correspondinglylow amount of constituent oxides useful for delivering bindingproperties (see Table 1 for an example chemical constitution of GPOFA).To remove the unburned carbon content and to provide an ash materialwith improved pozzolanic properties, the GPOFA is preferably calcined.The calcination may be performed in a furnace, for example, agas-powered furnace. The calcination may be performed using a pre-settemperature program or using other variable temperature systems known bythose of ordinary skill in the art. The GPOFA may be calcined underisothermal conditions or under variable temperature conditions,typically at a temperature range of 400 to 900° C., preferably 425 to850° C., preferably 450 to 800° C., more preferably 475 to 750° C.,preferably 500 to 700° C., preferably 550 to 600° C. The calcination istypically performed for 20 minutes to 8 hours, preferably 40 minutes to6 hours, preferably 60 minutes to 4 hours, preferably 80 minutes to 3hours, preferably 90 minutes to 2 hours, although shorter or longercalcination times may also be used herein.

While the calcined palm oil fuel ash may possess adequate bindingcapabilities when employed as a partial cement replacement, or in ablend (binary, ternary, etc.) with other binding materials (e.g., flyash, ground blast furnace slag, silica fume, metakaolin, etc.), it hasbeen discovered that subjecting the calcined palm oil fuel ash to asecond mechanical ball milling procedure provides a palm oil fuel ashproduct with the highest performance (referred to herein as treated palmoil fuel ash or “TPOFA”), which enables its use as a full cementreplacement, and without the need for additional binders. The parametersof the second ball milling procedure are as described for the first ballmilling procedure above. The parameters used (the type of equipment, thematerials used for the vials, the materials used for the balls, the ballsize, the BPR, the rotational speed, the milling time, the millingatmosphere) for the first ball milling and the second ball milling maybe the same, or different, preferably the parameters used for the firstand second ball milling operations are the same.

Treated palm oil fuel ash (TPOFA) may vary in terms of the percent ofconstituent oxides present depending on a number of factors, such as thetype of oil palm tree cultivated, the source/location of the oil palmtree cultivated, the relative proportion of the waste products (palm oilfibers, shells, and empty fruit brunches) combusted to produce the POFA,the combustion conditions, as well as the post-combustion processing,etc. The treated palm oil fuel ash used herein generally comprises,consists of, or consists essentially of, SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO,K₂O, SO₃, Na₂O, and P₂O₃. In preferred embodiments, the treated palm oilfuel ash utilized in the present disclosure has a total content of SiO₂,Al₂O₃, and Fe₂O₃ that complies with ASTM C618 class F standards forpozzolan, which is incorporated herein by reference in its entirety. Thepresent disclosure contemplates using a wide variety of treated palm oilfuel ash materials, with the following constitutional makeup beingpreferred.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of SiO₂ of 60 to 72 wt. %, preferably 61 to 71 wt. %,preferably 62 to 70 wt. %, preferably 63 to 69 wt. %, preferably 64 to68 wt. %, preferably 65 to 67.5 wt. %, preferably 66 to 67 wt. %, basedon a total weight of the treated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of Al₂O₃ of 4 to 8 wt. %, preferably 4.5 to 7.5 wt. %,preferably 5 to 7 wt. %, preferably 5.5 to 6.8 wt. %, preferably 6 to6.5 wt. %, based on a total weight of the treated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of Fe₂O₃ of 3 to 7 wt. %, preferably 3.5 to 6.5 wt. %,preferably 4 to 6.3 wt. %, preferably 4.5 to 6.1 wt. %, preferably 5 to6 wt. %, preferably 5.5 to 5.8 wt. %, based on a total weight of thetreated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of CaO of 3 to 8 wt. %, 3.5 to 7 wt. %, preferably 4 to 6.5wt. %, preferably 4.5 to 6.3 wt. %, preferably 5 to 6.1 wt. %,preferably 5.3 to 6 wt. %, preferably 5.5 to 5.8 wt. %, based on a totalweight of the treated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of MgO of 1 to 5 wt. %, preferably 1.5 to 4.5 wt. %,preferably 2 to 4 wt. %, preferably 2.5 to 3.8 wt. %, preferably 3 to3.5 wt. %, preferably 3.1 to 3.2 wt. %, based on a total weight of thetreated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of K₂O of 3 to 7 wt. %, preferably 3.5 to 6.5 wt. %,preferably 4 to 6 wt. %, preferably 4.5 to 5.8 wt. %, preferably 5 to5.4 wt. %, preferably 5.1 to 5.3 wt. %, based on a total weight of thetreated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of SO₃ of 0.2 to 0.5 wt. %, preferably 0.25 to 0.45 wt. %,preferably 0.3 to 0.4 wt. %, preferably 0.31 to 0.38 wt. %, preferably0.32 to 0.34 wt. %, based on a total weight of the treated palm oil fuelash.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of Na₂O of 0.1 to 0.25 wt. %, preferably 0.13 to 0.23 wt. %,preferably 0.15 to 0.22 wt. %, preferably 0.17 to 0.21 wt. %, preferably0.18 to 0.2 wt. %, based on a total weight of the treated palm oil fuelash.

In some embodiments, the treated palm oil fuel ash has a weightpercentage of P₂O₃ of 1 to 5 wt. %, preferably 2 to 4 wt. %, preferably3 to 3.8 wt. %, preferably 3.2 to 3.6 wt. %, preferably 3.3 to 3.5 wt.%, based on a total weight of the treated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash of the presentdisclosure has a loss on ignition (LOI) of less than 4 wt. %, preferablyless than 3 wt. %, preferably less than 2.5 wt. %, preferably less than2.4 wt. %, preferably less than or equal to 2.3 wt. %, based on a totalweight of the treated palm oil fuel ash.

In preferred embodiments, the treated palm oil fuel ash comprises, asconstituent oxides, 66 to 68 wt. % SiO₂, 6 to 7 wt. % Al₂O₃, 5 to 6.5wt. % Fe₂O₃, 5 to 6 wt. % CaO, 2.5 to 3.5 wt. % MgO, 4.5 to 6 wt. % K₂O,0.3 to 0.35 wt. % SO₃, 0.18 to 0.2 wt. % Na₂O, and 3 to 4 wt. % of P₂O₃,each based on a total weight of the treated palm oil fuel ash.

In some embodiments, the treated palm oil fuel ash has a median particlesize (d₅₀) of 0.5 to 2.0 μm, preferably 0.6 to 1.8 μm, preferably 0.7 to1.6 μm, preferably 0.8 to 1.4 μm, preferably 0.9 to 1.2 μm, preferably1.0 to 1.1 μm, preferably 1.068 μm.

In some embodiments, the treated palm oil fuel ash has a specificsurface area of 1.4 to 1.6 m²/g, preferably 1.45 to 1.58 m²/g,preferably 1.5 to 1.56 m²/g, preferably 1.51 to 1.54 m²/g, preferably1.52 to 1.53 m²/g.

The treated palm oil fuel ash may be used as a partial replacement ofcement, or may be used in combination with one or more other binders(discussed below) in a binder blend. Therefore, in such circumstances,the treated palm oil fuel ash may be employed in an amount of up to 30wt. %, preferably up to 25 wt. %, preferably up to 20 wt. %, preferablyup to 15 wt. %, preferably up to 10 wt. %, preferably up to 5 wt. %,preferably up to 1 wt. %, preferably up to 0.5 wt. %, based on a totalweight of the mortar composition. However, the treated palm oil fuel ashmay be advantageously employed as a complete cement replacement, andwherein the TPOFA is the only binder present. Thus, in preferredembodiments, the treated palm oil fuel ash is the only binder present,and is employed an amount of 20 to 30 wt. %, preferably 21 to 29 wt. %,preferably 22 to 28 wt. %, preferably 23 to 27 wt. %, preferably 24 to26 wt. %, preferably 25 wt. %, based on a total weight of the mortarcomposition.

In the present disclosure, other binders which may be optionallyincluded in the mortar composition, but which are preferably excludedfrom the mortar composition, include any cement and/or pozzolan/burnedorganic matter residues (other than TPOFA) capable of producingcement-like binding properties.

Exemplary cements may be any hydraulic cement or a non-hydraulic cement,for example, Ordinary Portland Cement (OPC) type I, type II, type III,type IV, type V, type Ia, type IIa, type Ma or a combination thereof (inaccordance with the ASTM CI50 standard); Portland fly ash cement;Portland Pozzolan cement; Portland silica fume cement; masonry cements;EMC cements; stuccos; plastic cements; expansive cements; white blendedcements; Pozzolan-lime cements; slag cements; slag-lime cements;supersulfated cements; calcium aluminate cements; calcium sulfoaluminatecements; geopolymer cements; Rosendale cements; polymer cement mortar;lime mortar; Pozzolana mortar; and the like, as well as mixturesthereof.

Exemplary pozzolanic and/or burned organic matter residues may include,but are not limited to, limestone; fly ash (e.g. siliceous fly ashand/or calcareous fly ash), for example Class C fly ash, Class F flyash, pulverized fly ash, ultrafine Class F fly ash; slag; ground blastfurnace slag (GGBFS or GGBS); cement kiln dust (CKD); silica fume orother fine forms of silica such as fine silica flour; metakaolin;vitreous calcium aluminosilicate (VCAS); carbon nanofibers and othercarbon products; calcium hydroxide (Ca(OH)₂); date palm ash or simply“palm ash”, which is produced as wastage during the production of palmfirewood and coal products (typically has a chemical constitution of30-40 wt % SiO₂, 0.1-1.0 wt % of Fe₂O₃, 10-15 wt % of CaO, 0.1-1.0 wt %of Al₂O₃, 5-10 wt % of MgO, 2-10 wt % of K₂O, and 1-5 wt % of Na₂O);burned palm oil products (other than palm oil fuel ash) such as oil palmshell (OPS); rice husk ash; volcanic ashes and pumices (e.g., crushedvolcanic glass); diatomaceous earth; synthetic pozzolans such assynthesized reactive aluminosilicate glasses; zeolite materials such ascalcined zeolites; cenospheres; pozzolana; calcined shale; trass;pumice; siliceous clays; metropolitan waste ash; sewerage ash; coal washtailings; mineral tailings; scoria; obsidian; other flue ashes; andother ash derived from burning organic waste.

Fine Aggregate

The mortar composition of the present disclosure may also include one ormore fine aggregates. The fine aggregate may include, but is not limitedto, sand (e.g., dune sand), crushed stone, crushed rock, crushed shells,or other crushed/pulverized/ground material, for example,crushed/pulverized/ground forms of concrete, gravel, rocks, naturalsoil, quarried crushed mineral aggregates from igneous (granite,syenite, diorite, gabbro peridotite pegmatite, volcanic glass, felsite,basalt), metamorphic (marble, metaquartzite, slate, phyllite, schist,amphibolite, hornfels, gneiss, serpentite) or sedimentary rocks(conglomerate, sandstone, claystone, siltstone, argillite, shale,limestone, dolomite, marl, chalk, chert), including unused and wasteaggregates from quarry operations, dredged aggregates, china clay stent,china clay wastes, natural stone, recycled bituminous pavements,recycled concrete pavements, reclaimed road base and subbase materials,crushed bricks, construction and demolition wastes, crushed glass, slatewaste, waste plastics, egg shells, sea shells, barite, limonite,magnetite, ilmenite, hematite, iron, steel, including recycled or scrapsteel, and mixtures thereof. In preferred embodiments, the fineaggregate employed in the mortar compositions is dune sand.

The amount of fine aggregate deployed herein may vary, but typically aweight ratio of the fine aggregate to the treated palm oil fuel ashranges from 1:1 to 2:1, preferably 1.1:1 to 1.9:1, preferably 1.2:1 to1.8:1, preferably 1.3:1 to 1.7:1, preferably 1.4:1 to 1.6:1, preferably1.5:1.

The fine aggregate may have an average particle size of 0.3 to 1 mm,preferably 0.4 to 0.8 mm, preferably 0.5 to 0.6 mm, although fineaggregates with average particle sizes slightly above or below thesevalues may also function as intended. The grading of fine aggregateemployed herein preferably conforms to the standard ASTM C 33/C33M-18,which is incorporated herein by reference in its entirety.

In preferred embodiments, the fine aggregate has a fineness modulus of1.8 to 2.1, preferably 1.81 to 2.0, preferably 1.82 to 1.9, preferably1.83 to 1.88, preferably 1.84 to 1.86, preferably 1.85. The Finenessmodulus (FM) is an empirically determined index of the fineness of anaggregate—the higher the FM, the coarser the aggregate. The finenessmodulus is obtained by adding the cumulative percentages by massretained on each of a specified series of sieves and dividing the sum by100. The specified sieves for determining the fineness modulus for fineaggregate are 0.15 mm, 0.3 mm, 0.6 mm, 1.18 mm, 2.36 mm, 4.75 mm, and9.5 mm, for example, according to ASTM C125 and ASTM C33/C33M-18.

In preferred embodiments, the fine aggregate has a saturated surface dry(SSD) specific gravity of 2.5 to 2.7, preferably 2.55 to 2.68,preferably 2.6 to 2.66, preferably 2.61 to 2.64, preferably 2.62.Saturated surface dry (SSD) is defined as the condition of an aggregatein which the surfaces of the particles are “dry” (i.e., surfaceadsorption would no longer take place), but the inter-particle voids aresaturated with water. In this condition aggregates will not affect thefree water content of a composite material. That is, SSD specificgravity is the ratio of the weight in air of a unit volume of aggregate,including the weight of water within the voids filled to the extentachieved by submerging in water for approximately 15 hours, and wherethe excess, free surface moisture has been removed so that the surfaceof the particle is essentially dry, to the weight in air of an equalvolume of gas-free distilled water at the stated temperature, forexample, according to AASHTO T 84.

While in some cases the mortar composition can be formulated to includea coarse aggregate, in preferred embodiments, the mortar composition issubstantially free of coarse aggregates.

Alkali Activator

An alkali activator must be included in the mortar composition. Alkaliactivation generally releases reactive species (e.g., CaO) from thebinder, thus increasing the rate of densification and improving themicrostructural strength of the binder, which by extension affects themechanical properties and durability performance of the cured mortar.The alkali activator may be a mixture of an aqueous solution of a metalhydroxide, preferably an alkali metal hydroxide (e.g., sodium hydroxide,potassium hydroxide, etc.), and a metal silicate, preferably an alkalimetal silicate (e.g., sodium silicate, potassium silicate, etc.). Insome embodiments, the alkali activator may be an aqueous solution of ametal hydroxide, preferably an alkali metal hydroxide.

In preferred embodiments, the alkali activator is an aqueous mixture ofsodium hydroxide and sodium silicate. Preferably, the alkali activatorconsists of sodium hydroxide and sodium silicate in water. A weightratio of sodium silicate to sodium hydroxide may generally range from1:1 to 3:1, preferably 1.2:1 to 2.9:1, preferably 1.4:1 to 2.8:1,preferably 1.6:1 to 2.7:1, preferably 1.8:1 to 2.6:1, preferably 2:1 to2.5:1. In some embodiments, the sodium silicate has a silica modulus(SiO₂:Na₂O weight ratio) of 1.5 to 4, preferably 2 to 3.8, preferably2.5 to 3.6, preferably 3 to 3.4, preferably 3.3. In some embodiments,the sodium hydroxide has a specific gravity of 2 to 2.4, preferably 2.05to 2.3, preferably 2.1 to 2.2, preferably 2.13.

In preferred embodiments, the mortar compositions are prepared using aweight ratio of the alkali activator to the treated palm oil fuel ash offrom 0.3:1 to 0.7:1, preferably 0.34:1 to 0.65:1, preferably 0.36:1 to0.6:1, preferably 0.38:1 to 0.55:1, preferably 0.4:1 to 0.5:1.

The way in which the alkali activator is prepared may also impact thefinal properties of the cured mortar. For example, the concentration ofthe sodium hydroxide used to prepare the alkali activator has been foundto impact the compressive strength of the cured mortar. Typically, thesodium hydroxide and sodium silicate are premixed in the form of anaqueous solution, and this aqueous alkali activator solution is thenadded to any dry components to form the mortar composition, as will bediscussed hereinafter. In this process, it has been found that use of anaqueous solution of sodium hydroxide having a concentration of 8 to 12mol/L, preferably 9 to 11 mol/L, preferably 10 mol/L, ultimatelyprovides cured mortars with superior compressive strength properties.Without being bound by theory, it is believed that such molarconcentrations of sodium hydroxide combines with the sodium silicate insuch a way that effects the rate of silica and alumina release from thepalm oil fuel ash material, and the enhanced dissolution produces curedmortar with superior strength characteristics (e.g., compressivestrength).

Strength Enhancer

The mortar composition of the present disclosure may also include astrength enhancer, preferably an aluminum-containing strength enhancer.In preferred embodiments, the strength enhancer is aluminum hydroxide(Al(OH)₃). Any amount of aluminum hydroxide may be employed herein thatprovides acceptable Al₂O₃ levels in the mortar compositions and,ultimately, strength properties to the cured mortar. In someembodiments, a weight ratio of the aluminum hydroxide to the treatedpalm oil fuel ash is 0.01:1 to 0.05:1, preferably 0.015:1 to 0.04:1,preferably 0.016:1 to 0.03:1, preferably 0.018:1 to 0.025:1, preferably0.02:1.

The mortar compositions may optionally include other strength enhancersbesides aluminum hydroxide, and such other strength enhancers aregenerally known to those of ordinary skill in the art, for example,sodium fluoride, potassium fluoride, sodium sulfate, sodium oxalate, analkali phosphate (e.g., sodium phosphate) and related compounds, just toname a few. However, in preferred embodiments, the mortar composition issubstantially free of all other strength enhancers other than aluminumhydroxide, i.e., aluminum hydroxide is the only strength enhancerpresent.

Water

The mortar composition also includes water. In some embodiments, theweight ratio of the water to the treated palm oil fuel ash is 0.2 to0.98, preferably 0.3 to 0.9, preferably 0.4 to 0.8, preferably 0.5 to0.7, preferably 0.55 to 0.6. It is normally advantageous in mortarcompositions to utilize an amount of water that provides a thick mixturefor easy application as a glue-like material for building materials suchas brick. However, a person of ordinary skill can adjust the watercontent of the mortar compositions as needed to suit the application orworkability requirements, and the water to binder (POFA) weight ratiomay therefore fall outside of these described ranges. Suitable watersources include fresh water, potable water, and the like, preferablypotable water.

Additives

In some embodiments, the mortar compositions optionally include one ormore additives such as an accelerator, a retarder, a plasticizer (e.g.,a superplasticizer), a pigment, a corrosion inhibitor, and a bondingagent, including mixtures thereof. The additional additive(s), whenpresent, may be present in an amount up to 5 wt. %, preferably up to 4wt. %, preferably up to 3 wt. %, preferably up to 2 wt. %, preferably upto 1 wt. %, preferably up to 0.5 wt. %, preferably up to 0.1 wt. %,preferably up to 0.05 wt. %, preferably up to 0.01 wt. %, based on thetotal weight of the mortar composition.

An accelerator is any chemical capable of accelerating the hardening(early strength development) of mortar. Suitable examples ofaccelerators that may be included in the mortar compositions hereininclude, but are not limited to, calcium nitrite, calcium nitrate,calcium formate, calcium chloride, sodium nitrate, or a combinationthereof.

A retarder is any chemical capable of retarding the hardening (earlystrength development) of mortar. Acceptable examples of retardersinclude, but are not limited to, a borate salt such as of sodiumpentaborate (Na₂B₁₀O₁₆), sodium tetraborate (Na₂B₄O₇) and boric acid(H₃BO₃); an organophosphonate such as sodium or calcium salts ofethylenediaminetetra (methylenephosphonic acid) (EDTMP),hexamethylenediaminetetra (methylenephosphonic acid), anddiethylenetriaminepenta (methylenephosphonic acid); acrylamidecopolymers such as copolymers formed from2-acrylamido-2-methylpropane-3-sulphonic acid (AMPS) and one or moreacrylic acid or non-sulfonated acrylamide monomers; metal sulfates suchas ferrous sulfate; gypsum; sugar; sucrose; sodium gluconate; glucose;citric acid; tartaric acid; and the like; as well as mixtures thereof.

Broadly, a plasticizer is a material that when added to another yields amixture which is easier to handle or has greater utility. Theplasticizer as used herein means an organic compound which is usuallynon-volatile at standard room temperature and pressure (25° C., 1 atm.)and which has no specific chemical reactivity. As such, the plasticizeris generally inert towards the binder and merely serves as a medium inwhich that binder may be suspended or otherwise dispersed. Suitableplasticizers may include, but are not limited to, polyalkyleneglycolsand other polyethers such as polyethylene glycol, polypropylene glycol,and polybutyleneglycol, including blends of two or more of suchpolyalkyleneglycols or blends of one or more of such polyalkyleneglycolswith one or more co-plasticizers, as well as phosphonic acid terminatedpolyalkylene glycols; sulfonated or phosphorylated organic compoundssuch as alkyl sulfonic acid esters of phenol and cresol (for exampleMESAMOLL from Lanxess) and aromatic sulfonamides; alkyl or aryl estersof organic acids such as benzoic acid esters of glycols and theiroligomers, esters of 1,2-dicarboxycyclohexane (hydrogenated phthalates),phthalic acid esters, terephthalic acid esters, trimellitates, adipicacid esters, sebasic acid esters, tartrate esters, citric acid estersand sucrose esters; oils which can be natural or synthetic, such asvegetable oils and their derivatives including fatty acid esters andepoxidized vegetable oils, organic liquids derived from wood and otherforest products like liquid rosin esters, hydrocarbon fluids such asmineral oil or paraffinic liquids, and silicones; vinyl polymers such aspolyisobutene, liquid polybutadiene, and polycarboxylates such aspolycarboxylate (polycarboxylic) ethers (PCE) made from polymers ofacrylic acid and/or maleic acid with ether side chains, for exampleETHACRYL products from Arkema or MASTERGLENIUM products from BASF;polyesters; formaldehyde (formalin) resins (condensates) such assulfonated naphthalene formaldehyde resin, sulfonated melamineformaldehyde resin, acetone formaldehyde resin, e.g., crosslinked PMS(polymelamine sulfonate) and crosslinked PNS (polynaphthalenesulfonate); and mixtures thereof.

One particular type of plasticizer known as superplasticizer (SP) may beoptionally employed in the disclosed mortar compositions.Superplasticizers are also known as high range water reducers, and areadditives generally used in making high strength mortar or concrete. Inpreferred embodiments, when present, the superplasticizer satisfies theASTM C494/C494M-17 requirements, which is incorporated herein byreference in its entirety. The superplasticizers that may be employed inthe present disclosure include, but are not limited to, polyalkylarylsulfonate superplasticizers, such as condensation products ofnaphthalene sulfonic acid with formalin or a salt thereof, acondensation product of methylnaphthalene sulfonic acid with formalin ora salt thereof, and a condensation product of anthracene sulfonic acidwith formalin or a salt thereof, for example, MIGHTY 100, MIGHTY 150,and MIGHTY 200 each available from KAO Corporation, and PANTARHIT FT-500available from Ha-Be Betonchemie; melamine/formalin resin sulfonatesuperplasticizers, for example MELMENT F-10 available from BASF;sulfonated copolymer superplasticizers such as styrene-α-methylstyrenecopolymers containing a mole ratio of from 90:10 to 10:90, preferably30:70 to 70:30, of styrene to α-methylstyrene; polycarboxylates, inparticular polycarboxylate ethers (PCE) such as those made fromcopolymerization of (meth)acrylic acids, maleic anhydride, maleic acidsor their salts, with polyoxyethylene (meth)acrylic esters or adducts ofpolyethylene derivatives to vinyl monomers, for example MELFLUX orMASTERGLENIUM products available from BASF; or any other plasticizersexhibiting strong tackiness and non-bleeding properties; includingmixtures thereof. In some embodiments, when present, thesuperplasticizer is a chloride-free superplasticizer. In preferredembodiments, when present, the superplasticizer is a sulfonatednaphthalene formalin resin.

Pigments may be optionally included in the mortar composition to formcolored cured mortars. Exemplary pigments include, but are not limitedto, iron oxide, natural burnt umber, carbon black, chromium oxide,ultra-marine blue, titanium dioxide, among many other pigments known tothose of ordinary skill in the art to provide mortars with desirablecolors.

The mortar compositions may optionally be formulated with corrosioninhibitors. Any corrosion inhibitor known to those of ordinary skill inthe art for use in mortar/concrete applications may be used herein, withspecific mention being made to nitrites (e.g. calcium nitrite),chromates, phosphates, benzotriazoles, alkanolamines (e.g.N,N-diethyl-ethanolamine, N-methyl-ethanolamine, monoethanloamine,diethanloamine, triethanloamine), including mixtures thereof.

Bonding agents may also be optionally included in the mortarcompositions. Exemplary bonding agents include, but are not limited to,aluminum sulfate, latex resins such as acrylic polymer latex resins,epoxy resins, vinyl polymer resins.

In some embodiments, the mortar composition is substantially free ofadditives. In some embodiments, the mortar composition is substantiallyfree of plasticizers, in particular, superplasticizers. In someembodiments, the mortar composition is substantially free oforganosilicon compounds. In some embodiments, the mortar compositionsare substantially free of synthetic polymers such as polyvinyl alcohol(PVA), including PVA fibers, either coated or uncoated. In someembodiments, the mortar composition is substantially free of foamingagents. In some embodiments, the mortar composition is substantiallyfree of defoamers. In preferred embodiments, the mortar compositionconsists of the treated palm oil fuel ash, the fine aggregate, sodiumhydroxide, sodium silicate, aluminum hydroxide, and water.

In some embodiments, the mortar composition has a workable flow,expressed as a percentage increase in the average base diameter of a 50mm cube mortar specimen after performing table drops compared to theoriginal base diameter, of 105 to 140%, preferably 110 to 135%,preferably 115 to 130%, preferably 120 to 125%, per ASTM C1437, which isincorporated herein by reference in its entirety.

Any method known by those of ordinary skill in the art may be used tomake the mortar composition of the present disclosure. One exemplarymethod will now be briefly described.

The mortar compositions of the present disclosure may be prepared byfirst dry-mixing the binder (e.g. treated palm oil fuel ash), the fineaggregate, the strength enhancer (e.g., aluminum hydroxide), and anysolid optional additives either by hand or using a mechanical mixer suchas a Hobart floor mixer for any time period suitable for removing airpockets and forming a uniform mixture of dry materials (dry mix).Typical mixing times may be around 0.5 to 10 minutes, preferably 1 to 5minutes, preferably 2 to 3 minutes. In some embodiments, such a dry mixmay obtained as a pre-formed and/or pre-packaged dry mix.

Next, the alkali activator (e.g., an aqueous mixture of sodium hydroxideand sodium silicate) may be added and the mixture may be mixed for 1 to10 minutes, preferably 3 to 8 minutes, preferably 5 to 6 minutes,although time periods outside of these ranges may also be acceptable.

In some embodiments, all of the water used to make the mortarcomposition comes from the addition of the alkali activator.Alternatively, in some instances it may be desirable to add additionalwater and/or any optional additive(s) after alkali activation to improvethe consistency/workable flow of the mortar composition or to otherwisechange the properties of the mortar composition/cured mortar. Whenadditional water and/or optional additive(s) are added, the mixture maybe preferably mixed for an additional 1 to 10 minutes, preferably 3 to 8minutes, preferably 4 to 5 minutes, or otherwise to provide an overallaverage mixing time of 8 to 16 minutes, preferably 10 to 14 minutes,preferably 12 minutes. Intermittently, the mixing operation may bestopped to remove any clumps of solid materials that stick to the bottomof the mixing vessel, and then mixing may be again continued until adesirable homogeneity and consistency of the mortar composition has beenachieved.

Of course, the relative amounts of the components may be adjusted at anypoint to achieve mortar compositions having the desired properties. Forexample the workable flow may be tested according to ASTM C1437 and therelative amounts of any component(s) (e.g., water, fine aggregate,binder, strength enhancer, and/or any optional additive(s)) may beadjusted as needed to be within desired specifications.

Cured Mortar

After forming the mortar composition, the mortar composition may bemolded, casted, placed, applied, compacted, and/or finished, and thencured (set) as needed to suit a particular application. For example, themortar composition may be placed in between construction materials andcured, applied to a surface such as a brick wall and cured to smoothensaid wall, etc.

Curing may be carried out under ambient conditions, for example 20 to35° C., preferably 23 to 30° C., preferably 25 to 28° C., or throughapplied heat, for example at temperatures of 50 to 70° C., preferably 55to 65° C., preferably 60° C. The cure times may vary from 1 day to 180days, for example, 3, 7, 14, 28, 90, 180 days and any time in betweenthose stated values, preferably 7 to 28 days.

In some embodiments, the cured mortar has a unit weight of 2200 to 2300kg/m³, preferably 2210 to 2290 kg/m³, preferably 2220 to 2280 kg/m³,preferably 2230 to 2270 kg/m³, preferably 2240 to 2260 kg/m³, preferably2250 kg/m³.

The mortar composition described herein provides cured mortar withexceptionally high compressive strength considering that cement ispreferably fully replaced with a waste product (i.e., treated palm oilfuel ash). The mortar composition provides, after curing/setting, acured mortar with 28-day compressive strength of 25 to 36 MPa,preferably 25.5 to 35.9 MPa, preferably 26 to 35.8 MPa, preferably 26.5to 35.7 MPa, preferably 27 to 35.6 MPa, preferably 27.5 to 35.5 MPa,preferably 28 to 35.4 MPa, preferably 28.5 to 35.3 MPa, preferably 29 to35.2 MPa, preferably 29.5 to 35.1 MPa, preferably 30 to 35 MPa. Allcompressive strength tests may be tested using 50 mm cubed mortarsamples according to ASTM C39, which is incorporated herein by referencein its entirety.

The disclosed mortar compositions may be useful in many structural andinfrastructural applications that utilize concrete, brick, or otherstructural element as building material, and in the manufacture ofvarious end use articles or products. For example, the cured mortar maybe applied to or otherwise used to form, slabs, panels, precast panels,wall boards, floor and roof tiles, catch basins, manholes, beams,columns, posts, conduits and pipes, insulators, external cladding,slate, concrete decking, e.g. swimming pools, surfaces and surrounds,ceramic style products, marble like products, sink tops, bar tops,bathroom tops, table tops, fireplace tiles, fire proof walls, buildingblocks (e.g. masonry blocks); both reinforced and not reinforced bysteel, depending on the use and purpose for which the manufacturedproducts are fabricated. In preferred embodiments, the cured mortardescribed herein possess sufficient mechanical properties for use inapplications described in ASTM C139, which is incorporated herein byreference in its entirety.

Having generally described this disclosure, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

Where a numerical limit or range is stated herein, the endpoints areincluded. Also, all values and subranges within a numerical limit orrange are specifically included as if explicitly written out.

The present disclosure also contemplates other embodiments “comprising”,“consisting of” and “consisting essentially of”, the embodiments orelements presented herein, whether explicitly set forth or not.

As used herein, the words “a” and “an” and the like carry the meaning of“one or more.”

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

All patents and other references mentioned above are incorporated infull herein by this reference, the same as if set forth at length.

EXAMPLES

Materials and Methods

Palm Oil Fuel Ash (POFA)

POFA was the only aluminosilicate source material and was obtained fromUnited Palm Oil Mill Sdn. Bhd. in Nibong Tebal, Penang, Malaysia. It isa by-product from the combustion of empty palm fruit bunches, palmkernel shells and fibers; normally used to heat the boiler forelectrical energy generation in the palm oil mill. FIG. 1 shows atypical dumping site for raw POFA, which is a combination of well-burntashes and partially burnt palm shells and fibers. The raw POFA particlesare predominantly dark in color due to the presence of high carbonamounts from incomplete burning of the residue. To adequately harnessthe inherent benefits of POFA, POFA was treated to remove unwantedresidue following the procedure highlighted in FIG. 2 . This wasachieved by drying the relatively moist raw POFA in an oven at 100±5° C.for 24 hours, as shown in FIG. 3 to remove the moisture and to allow forease of particles movement through the sieves. After drying, the driedPOFA was sieved through a set of sieves (600 μm and 300 μm) to removecoarser and unwanted materials. Subsequently, after sieving, the sievedPOFA was ground by a mechanical ball mill. The mechanical ball millshown in FIG. 4 has an approximately 7 kg-controlled capacity for eachcycle to achieve an efficient grinding of POFA. It holds 150 steel ballsof sizes ranging from 6 mm to 32 mm and rotating at speed of 180 rpm.Grinding was done to decrease the particle size of POFA and to increaseits surface area, which ultimately led to improved pozzolanicreactivity. At this stage, the POFA material is physically processed butnot thermally treated, hence referred to as ground POFA (GPOFA). Toremove unburnt carbon, prevent glassy phase crystallization andagglomeration of particles, the ground POFA was heated at 550° C. in agas-powered furnace for 90 min. After this calcination process, there isa change in color from black (ground POFA, FIG. 5 ) to grey (calcinedPOFA, FIG. 6 ) due to the removal of carbon responsible for the blackcolor. To further improve the surface area and specific gravity, thecalcined POFA is ground for another round in the ball mill to providetreated palm oil fuel ash (TPOFA). This is because the particlescharacterized by low specific gravity have had improved fineness andparticle size, hence increased specific gravity. The POFA treatmentprocedure adopted was due to the highest improvement achieved, which wasmeasured by the least amount of unburnt carbon content. The synthesis ofalkali-activation of POFA material will improve because of the carboncontent reduction. The loss on ignition (LOI) values reduced from 26% to2.3% after heat treatment, a sign of low unburnt residue in the POFA.The reduction in the LOI value is compensated for by an increase in themass percentages of other oxides.

The particle size distribution of the final stage of preparation of POFAwas determined using Laser Particle Sizer Analysette 22 MicroTec plusparticle size analyzer (PSA). The value of the surface area wasdetermined using Micromeritics ASAP2020 BET using nitrogen gasadsorption. Table 1 shows the oxide compositions and physical propertiesof TPOFA and GPOFA, which were determined using X-ray fluorescence (XRF)technique. With total oxides of silicon, aluminium and iron of 79.07%,the TPOFA complies with the specification of ASTM C618 class F (ASTMC618 2012).

TABLE 1 Chemical compositions and physical properties of TPOFA and GPOFAProperty Value Chemical TPOFA GPOFA Silicon dioxide (SiO₂), % 66.9162.74 Aluminum oxide (Al₂O₃), % 6.44 6.32 Ferric oxide (Fe₂O₃), % 5.724.87 Calcium oxide (CaO), % 5.56 4.94 Magnesium oxide (MgO), % 3.13 2.51Sodium oxide (Na₂O), % 0.19 0.15 Potassium oxide (K₂O), % 5.20 4.69Sulfur oxide (SO₃), % 0.33 0.26 Phosphorus (P₂O₃), % 3.41 3.72 LOI, %2.3 10.13 Physical Specific gravity (g/cm³) 2.53 2.87 Median particlesize d₅₀(μm) 1.068 2.96 Specific surface area (m²/g) 1.521 1.683Alkaline Activators

A mixed solution of NaOH_((aq)) and Na₂SiO₃ was used as an activator inthe developed alkali-activated mortar (AAM). Sodium hydroxide is cheapmaterial and it is widely available, making it a choice activator in thealkaline activation of the precursor material, in this case POFA.However, the corrosive nature of the highly alkaline alkali hydroxidespresents handling issues. Commercial grade sodium hydroxide pellets with97% purity and specific gravity of 2.13 were used in the preparation ofsodium hydroxide solution. The NaOH_((aq)) solution was prepared bydissolving either the flakes or pellets in water. The mass of NaOHsolids (flakes or pellets or in a solution) varied depending on theconcentration of the solution expressed in terms of desired molarity ofthe solution. For example, 8M NaOH solution was prepared by dissolving319.976 g of NaOH (in flake or pellet form) in one liter of distilledwater.

Sodium silicate (Na₂SiO₃), also known as water glass, was also used incombination with NaOH as an alkali activator. The silica modulus(SiO₂-to-Na₂O (or K₂O) ratio) varies from 1.5 to 4. The hydrates ofNa₂SiO₃ have the formula Na₂SiO₃·nH₂O where n=5, 6, 8, or 9. Availablewater glass has a silica modulus of 3.3 and holds 36-38% solids.

Water

Potable water, whose physiochemical composition shown in Table 2, wasused in the developed alkali-activated mortar.

TABLE 2 Physicochemical analysis of potable water used AnalysisAnalytical Methods Limits* Results Color Spectrometric 5.0 TCU <1 TCUTurbidity Photometric 5.0 NTU <1 NTU pH @ 25 deg C. Electrometric 5 to 7<1 to 7 Chloride Argentometric 250 mg/L <1 mg/L Iron Photometric(Phematroline method) 1.0 mg/L <0.05 mg/L Manganese Photometric(Persulfate method) 0.4 mg/L <0.01 mg/L Sulfate Photometric 250 mg/L <25mg/L Nitrate Photometric (Diazotization) 50 mg/L <1 mg/L Lead Directflame 0.01 mg/L <0.007 mg/L Arsenic Hydride generation 0.05 mg/L <0.01mg/L Cadmium Direct flame 0.003 mg/L <0.002 mg/L Total Dissolved SolidsGravimetric 500 mg/L <6 mg/L Limits* means recommended contaminantlevelsFine Aggregate

In the design of alkali-activated mortar/concrete, selection ofaggregate is important as most of the matrix volume is occupied byaggregates. The gradation of fine aggregate as shown in FIG. 7 meets therequirement specified in ASTM C33/C33M-18 (2018). The fine aggregateused was dune sand with fineness modulus of 1.85 and specific gravity inthe saturated and surface dry (SSD) condition of 2.62.

Superplasticizer

A commercially available polycarboxylic ether based superplasticizer(SP), MASTERGLENIUM 51, available from BASF, satisfying the ASTMC494/C494M-17 (2017) was used to modify the workability and to achieveadequate rheological properties of the developed alkali-activatedmortar. It is a chloride-free super plasticizing admixture.

Mixture Proportioning

The alkali-activated mortar mixture in Table 3 was prepared with 100%POFA as the binder with a constant fine aggregate (FA)/POFA ratio of1.5. The alkaline activators used were prepared from a mixture ofNaOH_((aq))(NH) and Na₂SiO_(3(aq)) (NS) with activator's relativeproportion—(Na₂SiO_(3(aq))/xM NaOH_((aq)): [x=10, 12 and 14 M]) whoseratios are 2.5, 2 and 1. The NaOH pellets were measured beforedissolution and placed in a beaker depending on the required molarity;distilled water was then added and thoroughly mixed. For instance, 10 MNaOH_((aq)) is prepared by measuring 399.97 g of NaOH pellets into abeaker and distilled water added to the 1000 ml mark on the beaker. Thesolution, which is exothermic, is stirred until all the pellets havedissolved and a clear solution obtained. After preparation, the solutionis allowed to cool down to prevent the alkaline activation process fromthermal interference from the exothermic NaOH_((aq)) solution. Based onthe alkali activator ratio, the Na₂SiO_(3(aq)) solution was added to themeasured NaOH_((aq)) solution and then mixed for several minutes.

TABLE 3 Mixture design for the developed mortar with Al(OH)₃ Al(OH)₃/Mixtures NS/NH (NS + NH)/POFA Sand/POFA Molarity POFA M1 2.5 0.4 1.5 100.02 M2 2.5 0.5 1.5 10 0.02 M3 2.5 0.6 1.5 10 0.02 M4 2 0.4 1.5 10 0.02M5 2.5 0.4 1.5 12 0.02 M6 2 0.4 1.5 12 0.02Mixing Procedure

An approximate unit weight of between 2200-2300 kg/m³ for the POFAalkali-activated mortar is quite comparable to that of typical Portlandcement concrete. Two stages of mixing were carried out; firstly, POFA,sand and Al(OH)₃ (for the control mixtures, Al(OH)₃ was absent) werethoroughly dry-mixed to remove air pockets using a Hobart floor mixerfor 2 minutes to get a uniform mixture of dry materials. Secondly, amixture of Na₂SiO_(3(aq)) (NS) and NaOH_((aq)) (NH) was added, allowedto mix for 5 mins and then water and/or superplasticizer was added toimprove its consistency. The mixture was allowed to mix for another 4-5mins making the overall average mixing time to be approximately 12 mins.Intermittently, the mixer was stopped to scrap manually the solidmaterials sticking to the bottom of the bowl. The mixing was continuedand was stopped when homogeneity and consistency of the mortar mixturehad been reached after 1-2 mins. As the flowability was important forthe fresh POFA AAM mixture, workability was assessed using the flowtable test. After ensuring a workable mixture, two layers of freshmortar were cast into 50 mm oil-smeared cubic molds. The mold wasvibrated for each layer of two for 15 s, after which the molds werewrapped in polythene sheets to reduce moisture loss.

Casting and Curing of Mortar Specimens

For the compressive strength, the mixtures were cast in two layers into50 mm×50 mm×50 mm oil smeared steel molds. Each layer was compacted on avibrating table for 1-2 mins after which the fresh POFA alkali-activatedmortar (POFA-engineered cementitious composite (EACC)) samples werecovered in vinyl bags to prevent moisture loss and left in thelaboratory at 25° C. for 24 hours prior to demolding. The specimens weredemolded and placed in vinyl plastic bags prior to curing in an oven at60±5° C. for 24 h. This was to aid in the alkaline activation reactionfor early strength increase. After the heat curing, the hardened sampleswere subsequently allowed to cool down in the laboratory untilpredetermined ages for the test. The same procedures were adopted forthe tensile and flexural strength specimens.

Test Methods

The optimized POFA alkali-activated concrete specimens were prepared andevaluated to determine the following properties according to standardprocedures at appropriate curing periods.

-   -   i) In accordance to ASTM C1437, the fresh properties (workable        flow) of the POFA alkali-activated mortar was determined using a        flow table test on 50 mm cube specimens of the POFA        alkali-activated mortar.    -   ii) In accordance to ASTM C39, the compressive strength of 50 mm        POFA alkali-activated mortar cube specimens after 7 and 28 days        of curing was measured.        Results and Discussion        Fresh Properties of POFA Alkali-Activated Mortar

The fresh properties of the POFA alkali-activated mortar were determinedin order to study the effects of water and the commercialsuperplasticizer (SP) to guide the choice of water or SP in otherexperimental mixtures. The workable flow spread of mortar was in therange of 110-135±5% for both water and SP, so we settled for water dueto cost. In addition, the spread values qualify the mixtures forhardened properties evaluation.

Compressive Strength of POFA Alkali-Activated Mortar

For the compressive strength of the hardened POFA alkali-activatedmortar, three different age (3, 14, and 28 days) records were taken tostudy the influence of time on the strength development. As shown inTable 4, the developed POFA alkali-activated mortar without Al(OH)₃achieved a minimum and maximum 28-day compressive strength of 23 and 25MPa, respectively. Upon the addition of Al(OH)₃, there was anapproximately 35% increase in strength with 2% addition of Al(OH)₃ inone of the mixtures (M4 in Table 4). This is very much dependent onsodium hydroxide concentration, sodium silicate to sodium hydroxideratio, alkaline activator/POFA ratio, sand/POFA and the chemicalproperties of POFA as a binder. Upon the modest addition of Al(OH)₃,there was an adjustment particularly in the Al₂O₃ content of POFAmaterial, which directly led to the microstructural transformation ofthe POFA binder as the percentage of Al(OH)₃ increases. Themicrostructural transformations were advantageous with modest additionof Al(OH)₃, however, became non-beneficial as the addition of Al(OH)₃increases. This is beneficial economically for the invention as the costof the mortar even with the Al(OH)₃ strength enhancer is still wellbelow the cost incurred in the production of OPC containingmortars/concretes.

TABLE 4 Compressive strength of the developed alkali-activated mortarwith or without Al(OH)₃ (NS + NH)/ Sand/ Al(OH)₃/ Without With %Mixtures NS/NH POFA POFA Molarity POFA Al(OH)₃ Al(OH)₃ Increase M1 2.50.4 1.5 10 0.02 25.14 30.07 16.40 M2 2.5 0.5 1.5 10 0.02 23.83 30.4621.78 M3 2.5 0.6 1.5 10 0.02 23.33 26.56 12.18 M4 2 0.4 1.5 10 0.0223.17 35.53 34.78 M5 2.5 0.4 1.5 12 0.02 24.96 31.24 20.11 M6 2 0.4 1.512 0.02 24.22 25.00 3.12Merits of the Developed Alkali-Activated Mortar

-   -   I. The palm oil fuel ash (POFA) alkali-activated mortar        (improved with Al(OH)₃) of the present disclosure comes        low-priced in comparison with the cost of OPC mortar or        concrete, and can be used in structural and infrastructural        applications.    -   II. With respect to the environment, the palm oil fuel ash        (POFA) alkali-activated mortar (improved with Al(OH)₃) of the        present disclosure is sustainable and eco-friendly due to the        huge availability of POFA and significantly low carbon footprint        in line with the requirements of the UN sustainable development        goal number 13.    -   III. With respect to United Nation sustainable development        goals, the use of POFA reduces not only the cost of materials        but also significantly reduces the carbon footprint because of        the complete replacement of Portland cement as cementitious        binder.    -   IV. The beneficial use of POFA agricultural wastes in the        invention conserves hectares of lands currently used for        landfills, allowing the lands to be used constructively, e.g.,        for the development of roads, buildings etc.    -   V. The POFA aluminosilicate materials used in the development        mortar moved from being a harmful landfill material to a        beneficial material used in the invention.    -   VI. The mortar of the present disclosure proved to have        excellent fresh and hardened properties, in some case achieving        a compressive strength of almost 36 MPa when enhanced with a        modest percentage of Al(OH)₃. Bearing in mind this is mortar and        not concrete, the achieved strength is high and impressive for        mortar.

The invention claimed is:
 1. An iron oxide-containing mortarcomposition, comprising: a treated palm oil fuel ash as a binder,wherein the treated palm oil fuel ash is the only binder present and hasa median particle size (d₅₀) of 0.5 to 2.0 μm and contains Fe₂O₃ in anamount of 3 to 7 wt. % based on the total weight of the treated palm oilfuel ash; a fine aggregate; an alkali activator comprising an aqueoussolution of sodium hydroxide and sodium silicate; and aluminum hydroxideas a strength enhancer, wherein the aluminum hydroxide is the onlystrength enhancer present, and wherein a weight ratio of the aluminumhydroxide to the treated palm oil fuel ash is 0.01:1 to 0.05:1.
 2. Themortar composition of claim 1, wherein the treated palm oil fuel ash ispresent in an amount of 20 to 30 wt. %, based on a total weight of themortar composition.
 3. The mortar composition of claim 1, wherein thetreated palm oil fuel ash comprises, as constituent oxides, 66 to 68 wt.% SiO₂, 6 to 7 wt. % Al₂O₃, 5 to 6.5 wt. % Fe₂O₃, 5 to 6 wt. % CaO, 2.5to 3.5 wt. % MgO, 4.5 to 6 wt. % K₂O, 0.3 to 0.35 wt. % SO₃, 0.18 to 0.2wt. % Na₂O, and 3 to 4 wt. % of P₂O₃, each based on a total weight ofthe treated palm oil fuel ash.
 4. The mortar composition of claim 1,wherein a weight ratio of the fine aggregate to the treated palm oilfuel ash is 1:1 to 2:1.
 5. The mortar composition of claim 1, which hasweight ratio of water to the treated palm oil fuel ash of 0.2 to 0.98.6. The mortar composition of claim 1, which consists of the treated palmoil fuel ash, the fine aggregate, sodium hydroxide, sodium silicate,aluminum hydroxide, and water.